The effect of social experience on olfactory preference in male mice

Since olfaction plays a primary role in rodent social interaction, the olfactory preference test (OPT) is one of the most widely used behavioural tests. However, behavioural tests require specific experimental design and can easily be affected by environmental factors. Here, we discuss the effect of social experience on male mouse behaviour in the OPT. In the present study, we assessed olfactory preference of male mice towards male or female soiled bedding. Each male mouse was allowed to investigate two Petri dishes containing soiled bedding for 5 min. We used four groups of animals differing in terms of social experience before the OPT: naïve males (Naïve), sexually experienced males (SE), males that had experienced 24 h of contact with females (FE), and males that had experienced a 15-min contact period with both male and female intruders. Our data indicate that sexually experienced males show a reproducible female smell preference (mean female sniffing (mean F) = 71.56% ± 2.59%, mean male sniffing (mean M) = 28.44% ± 2.59%, p < 0.001). Naïve males exhibited no bedding preference at all (mean F = 51.30% ± 2.79%, mean M = 48.70% ± 2.79%). Males that experienced contact with females (FE) also showed no odour preference (mean F = 44.13% ± 3.74%, mean M = 55.87% ± 3.74%). Interaction with male and female intruders for 15 min resulted in a significant shift of odour preference to female odour in 50% of the test groups (group #1: mean F = 67.61% ± 2.58%, mean M = 32.39% ± 2.58%, p < 0.001, group #2: mean F = 62.58% ± 3.75%, mean M = 37.42% ± 3.75%, p < 0.05, group #3: mean F = 49.80% ± 2.34%, mean M = 50.20% ± 2.34%, group #4: mean F = 52.80% ± 3.42%, mean M = 47.20% ± 3.42%). Thus, this interaction can hardly evoke reproducible results in subsequent OPTs. Of all experimental setups tested, only sexual experience provides a consistent outcome of the OPT.